1 // SPDX-License-Identifier: GPL-2.0-only
3 * Framework for buffer objects that can be shared across devices/subsystems.
5 * Copyright(C) 2011 Linaro Limited. All rights reserved.
6 * Author: Sumit Semwal <sumit.semwal@ti.com>
8 * Many thanks to linaro-mm-sig list, and specially
9 * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
10 * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
11 * refining of this idea.
15 #include <linux/slab.h>
16 #include <linux/dma-buf.h>
17 #include <linux/dma-fence.h>
18 #include <linux/anon_inodes.h>
19 #include <linux/export.h>
20 #include <linux/debugfs.h>
21 #include <linux/module.h>
22 #include <linux/seq_file.h>
23 #include <linux/sync_file.h>
24 #include <linux/poll.h>
25 #include <linux/dma-resv.h>
27 #include <linux/mount.h>
28 #include <linux/pseudo_fs.h>
30 #include <uapi/linux/dma-buf.h>
31 #include <uapi/linux/magic.h>
33 #include "dma-buf-sysfs-stats.h"
35 static inline int is_dma_buf_file(struct file *);
38 struct list_head head;
42 static struct dma_buf_list db_list;
44 static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
46 struct dma_buf *dmabuf;
47 char name[DMA_BUF_NAME_LEN];
50 dmabuf = dentry->d_fsdata;
51 spin_lock(&dmabuf->name_lock);
53 ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
54 spin_unlock(&dmabuf->name_lock);
56 return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
57 dentry->d_name.name, ret > 0 ? name : "");
60 static void dma_buf_release(struct dentry *dentry)
62 struct dma_buf *dmabuf;
64 dmabuf = dentry->d_fsdata;
65 if (unlikely(!dmabuf))
68 BUG_ON(dmabuf->vmapping_counter);
71 * If you hit this BUG() it could mean:
72 * * There's a file reference imbalance in dma_buf_poll / dma_buf_poll_cb or somewhere else
73 * * dmabuf->cb_in/out.active are non-0 despite no pending fence callback
75 BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);
77 dma_buf_stats_teardown(dmabuf);
78 dmabuf->ops->release(dmabuf);
80 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
81 dma_resv_fini(dmabuf->resv);
83 WARN_ON(!list_empty(&dmabuf->attachments));
84 module_put(dmabuf->owner);
89 static int dma_buf_file_release(struct inode *inode, struct file *file)
91 struct dma_buf *dmabuf;
93 if (!is_dma_buf_file(file))
96 dmabuf = file->private_data;
98 mutex_lock(&db_list.lock);
99 list_del(&dmabuf->list_node);
100 mutex_unlock(&db_list.lock);
105 static const struct dentry_operations dma_buf_dentry_ops = {
106 .d_dname = dmabuffs_dname,
107 .d_release = dma_buf_release,
110 static struct vfsmount *dma_buf_mnt;
112 static int dma_buf_fs_init_context(struct fs_context *fc)
114 struct pseudo_fs_context *ctx;
116 ctx = init_pseudo(fc, DMA_BUF_MAGIC);
119 ctx->dops = &dma_buf_dentry_ops;
123 static struct file_system_type dma_buf_fs_type = {
125 .init_fs_context = dma_buf_fs_init_context,
126 .kill_sb = kill_anon_super,
129 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
131 struct dma_buf *dmabuf;
133 if (!is_dma_buf_file(file))
136 dmabuf = file->private_data;
138 /* check if buffer supports mmap */
139 if (!dmabuf->ops->mmap)
142 /* check for overflowing the buffer's size */
143 if (vma->vm_pgoff + vma_pages(vma) >
144 dmabuf->size >> PAGE_SHIFT)
147 return dmabuf->ops->mmap(dmabuf, vma);
150 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
152 struct dma_buf *dmabuf;
155 if (!is_dma_buf_file(file))
158 dmabuf = file->private_data;
160 /* only support discovering the end of the buffer,
161 but also allow SEEK_SET to maintain the idiomatic
162 SEEK_END(0), SEEK_CUR(0) pattern */
163 if (whence == SEEK_END)
165 else if (whence == SEEK_SET)
173 return base + offset;
177 * DOC: implicit fence polling
179 * To support cross-device and cross-driver synchronization of buffer access
180 * implicit fences (represented internally in the kernel with &struct dma_fence)
181 * can be attached to a &dma_buf. The glue for that and a few related things are
182 * provided in the &dma_resv structure.
184 * Userspace can query the state of these implicitly tracked fences using poll()
185 * and related system calls:
187 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
188 * most recent write or exclusive fence.
190 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
191 * all attached fences, shared and exclusive ones.
193 * Note that this only signals the completion of the respective fences, i.e. the
194 * DMA transfers are complete. Cache flushing and any other necessary
195 * preparations before CPU access can begin still need to happen.
197 * As an alternative to poll(), the set of fences on DMA buffer can be
198 * exported as a &sync_file using &dma_buf_sync_file_export.
201 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
203 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
204 struct dma_buf *dmabuf = container_of(dcb->poll, struct dma_buf, poll);
207 spin_lock_irqsave(&dcb->poll->lock, flags);
208 wake_up_locked_poll(dcb->poll, dcb->active);
210 spin_unlock_irqrestore(&dcb->poll->lock, flags);
211 dma_fence_put(fence);
212 /* Paired with get_file in dma_buf_poll */
216 static bool dma_buf_poll_add_cb(struct dma_resv *resv, bool write,
217 struct dma_buf_poll_cb_t *dcb)
219 struct dma_resv_iter cursor;
220 struct dma_fence *fence;
223 dma_resv_for_each_fence(&cursor, resv, dma_resv_usage_rw(write),
225 dma_fence_get(fence);
226 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb);
229 dma_fence_put(fence);
235 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
237 struct dma_buf *dmabuf;
238 struct dma_resv *resv;
241 dmabuf = file->private_data;
242 if (!dmabuf || !dmabuf->resv)
247 poll_wait(file, &dmabuf->poll, poll);
249 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
253 dma_resv_lock(resv, NULL);
255 if (events & EPOLLOUT) {
256 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out;
258 /* Check that callback isn't busy */
259 spin_lock_irq(&dmabuf->poll.lock);
263 dcb->active = EPOLLOUT;
264 spin_unlock_irq(&dmabuf->poll.lock);
266 if (events & EPOLLOUT) {
267 /* Paired with fput in dma_buf_poll_cb */
268 get_file(dmabuf->file);
270 if (!dma_buf_poll_add_cb(resv, true, dcb))
271 /* No callback queued, wake up any other waiters */
272 dma_buf_poll_cb(NULL, &dcb->cb);
278 if (events & EPOLLIN) {
279 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in;
281 /* Check that callback isn't busy */
282 spin_lock_irq(&dmabuf->poll.lock);
286 dcb->active = EPOLLIN;
287 spin_unlock_irq(&dmabuf->poll.lock);
289 if (events & EPOLLIN) {
290 /* Paired with fput in dma_buf_poll_cb */
291 get_file(dmabuf->file);
293 if (!dma_buf_poll_add_cb(resv, false, dcb))
294 /* No callback queued, wake up any other waiters */
295 dma_buf_poll_cb(NULL, &dcb->cb);
301 dma_resv_unlock(resv);
306 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
307 * It could support changing the name of the dma-buf if the same
308 * piece of memory is used for multiple purpose between different devices.
310 * @dmabuf: [in] dmabuf buffer that will be renamed.
311 * @buf: [in] A piece of userspace memory that contains the name of
314 * Returns 0 on success. If the dma-buf buffer is already attached to
315 * devices, return -EBUSY.
318 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
320 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
323 return PTR_ERR(name);
325 spin_lock(&dmabuf->name_lock);
328 spin_unlock(&dmabuf->name_lock);
333 #if IS_ENABLED(CONFIG_SYNC_FILE)
334 static long dma_buf_export_sync_file(struct dma_buf *dmabuf,
335 void __user *user_data)
337 struct dma_buf_export_sync_file arg;
338 enum dma_resv_usage usage;
339 struct dma_fence *fence = NULL;
340 struct sync_file *sync_file;
343 if (copy_from_user(&arg, user_data, sizeof(arg)))
346 if (arg.flags & ~DMA_BUF_SYNC_RW)
349 if ((arg.flags & DMA_BUF_SYNC_RW) == 0)
352 fd = get_unused_fd_flags(O_CLOEXEC);
356 usage = dma_resv_usage_rw(arg.flags & DMA_BUF_SYNC_WRITE);
357 ret = dma_resv_get_singleton(dmabuf->resv, usage, &fence);
362 fence = dma_fence_get_stub();
364 sync_file = sync_file_create(fence);
366 dma_fence_put(fence);
374 if (copy_to_user(user_data, &arg, sizeof(arg))) {
379 fd_install(fd, sync_file->file);
384 fput(sync_file->file);
390 static long dma_buf_import_sync_file(struct dma_buf *dmabuf,
391 const void __user *user_data)
393 struct dma_buf_import_sync_file arg;
394 struct dma_fence *fence;
395 enum dma_resv_usage usage;
398 if (copy_from_user(&arg, user_data, sizeof(arg)))
401 if (arg.flags & ~DMA_BUF_SYNC_RW)
404 if ((arg.flags & DMA_BUF_SYNC_RW) == 0)
407 fence = sync_file_get_fence(arg.fd);
411 usage = (arg.flags & DMA_BUF_SYNC_WRITE) ? DMA_RESV_USAGE_WRITE :
414 dma_resv_lock(dmabuf->resv, NULL);
416 ret = dma_resv_reserve_fences(dmabuf->resv, 1);
418 dma_resv_add_fence(dmabuf->resv, fence, usage);
420 dma_resv_unlock(dmabuf->resv);
422 dma_fence_put(fence);
428 static long dma_buf_ioctl(struct file *file,
429 unsigned int cmd, unsigned long arg)
431 struct dma_buf *dmabuf;
432 struct dma_buf_sync sync;
433 enum dma_data_direction direction;
436 dmabuf = file->private_data;
439 case DMA_BUF_IOCTL_SYNC:
440 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
443 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
446 switch (sync.flags & DMA_BUF_SYNC_RW) {
447 case DMA_BUF_SYNC_READ:
448 direction = DMA_FROM_DEVICE;
450 case DMA_BUF_SYNC_WRITE:
451 direction = DMA_TO_DEVICE;
453 case DMA_BUF_SYNC_RW:
454 direction = DMA_BIDIRECTIONAL;
460 if (sync.flags & DMA_BUF_SYNC_END)
461 ret = dma_buf_end_cpu_access(dmabuf, direction);
463 ret = dma_buf_begin_cpu_access(dmabuf, direction);
467 case DMA_BUF_SET_NAME_A:
468 case DMA_BUF_SET_NAME_B:
469 return dma_buf_set_name(dmabuf, (const char __user *)arg);
471 #if IS_ENABLED(CONFIG_SYNC_FILE)
472 case DMA_BUF_IOCTL_EXPORT_SYNC_FILE:
473 return dma_buf_export_sync_file(dmabuf, (void __user *)arg);
474 case DMA_BUF_IOCTL_IMPORT_SYNC_FILE:
475 return dma_buf_import_sync_file(dmabuf, (const void __user *)arg);
483 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
485 struct dma_buf *dmabuf = file->private_data;
487 seq_printf(m, "size:\t%zu\n", dmabuf->size);
488 /* Don't count the temporary reference taken inside procfs seq_show */
489 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
490 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
491 spin_lock(&dmabuf->name_lock);
493 seq_printf(m, "name:\t%s\n", dmabuf->name);
494 spin_unlock(&dmabuf->name_lock);
497 static const struct file_operations dma_buf_fops = {
498 .release = dma_buf_file_release,
499 .mmap = dma_buf_mmap_internal,
500 .llseek = dma_buf_llseek,
501 .poll = dma_buf_poll,
502 .unlocked_ioctl = dma_buf_ioctl,
503 .compat_ioctl = compat_ptr_ioctl,
504 .show_fdinfo = dma_buf_show_fdinfo,
508 * is_dma_buf_file - Check if struct file* is associated with dma_buf
510 static inline int is_dma_buf_file(struct file *file)
512 return file->f_op == &dma_buf_fops;
515 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
517 static atomic64_t dmabuf_inode = ATOMIC64_INIT(0);
519 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
522 return ERR_CAST(inode);
524 inode->i_size = dmabuf->size;
525 inode_set_bytes(inode, dmabuf->size);
528 * The ->i_ino acquired from get_next_ino() is not unique thus
529 * not suitable for using it as dentry name by dmabuf stats.
530 * Override ->i_ino with the unique and dmabuffs specific
533 inode->i_ino = atomic64_add_return(1, &dmabuf_inode);
534 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
535 flags, &dma_buf_fops);
538 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
539 file->private_data = dmabuf;
540 file->f_path.dentry->d_fsdata = dmabuf;
550 * DOC: dma buf device access
552 * For device DMA access to a shared DMA buffer the usual sequence of operations
555 * 1. The exporter defines his exporter instance using
556 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
557 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
558 * as a file descriptor by calling dma_buf_fd().
560 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
561 * to share with: First the file descriptor is converted to a &dma_buf using
562 * dma_buf_get(). Then the buffer is attached to the device using
565 * Up to this stage the exporter is still free to migrate or reallocate the
568 * 3. Once the buffer is attached to all devices userspace can initiate DMA
569 * access to the shared buffer. In the kernel this is done by calling
570 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
572 * 4. Once a driver is done with a shared buffer it needs to call
573 * dma_buf_detach() (after cleaning up any mappings) and then release the
574 * reference acquired with dma_buf_get() by calling dma_buf_put().
576 * For the detailed semantics exporters are expected to implement see
581 * dma_buf_export - Creates a new dma_buf, and associates an anon file
582 * with this buffer, so it can be exported.
583 * Also connect the allocator specific data and ops to the buffer.
584 * Additionally, provide a name string for exporter; useful in debugging.
586 * @exp_info: [in] holds all the export related information provided
587 * by the exporter. see &struct dma_buf_export_info
588 * for further details.
590 * Returns, on success, a newly created struct dma_buf object, which wraps the
591 * supplied private data and operations for struct dma_buf_ops. On either
592 * missing ops, or error in allocating struct dma_buf, will return negative
595 * For most cases the easiest way to create @exp_info is through the
596 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
598 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
600 struct dma_buf *dmabuf;
601 struct dma_resv *resv = exp_info->resv;
603 size_t alloc_size = sizeof(struct dma_buf);
607 alloc_size += sizeof(struct dma_resv);
609 /* prevent &dma_buf[1] == dma_buf->resv */
612 if (WARN_ON(!exp_info->priv
614 || !exp_info->ops->map_dma_buf
615 || !exp_info->ops->unmap_dma_buf
616 || !exp_info->ops->release)) {
617 return ERR_PTR(-EINVAL);
620 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
621 (exp_info->ops->pin || exp_info->ops->unpin)))
622 return ERR_PTR(-EINVAL);
624 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
625 return ERR_PTR(-EINVAL);
627 if (!try_module_get(exp_info->owner))
628 return ERR_PTR(-ENOENT);
630 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
636 dmabuf->priv = exp_info->priv;
637 dmabuf->ops = exp_info->ops;
638 dmabuf->size = exp_info->size;
639 dmabuf->exp_name = exp_info->exp_name;
640 dmabuf->owner = exp_info->owner;
641 spin_lock_init(&dmabuf->name_lock);
642 init_waitqueue_head(&dmabuf->poll);
643 dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll;
644 dmabuf->cb_in.active = dmabuf->cb_out.active = 0;
647 resv = (struct dma_resv *)&dmabuf[1];
652 file = dma_buf_getfile(dmabuf, exp_info->flags);
658 file->f_mode |= FMODE_LSEEK;
661 mutex_init(&dmabuf->lock);
662 INIT_LIST_HEAD(&dmabuf->attachments);
664 mutex_lock(&db_list.lock);
665 list_add(&dmabuf->list_node, &db_list.head);
666 mutex_unlock(&db_list.lock);
668 ret = dma_buf_stats_setup(dmabuf);
676 * Set file->f_path.dentry->d_fsdata to NULL so that when
677 * dma_buf_release() gets invoked by dentry_ops, it exits
678 * early before calling the release() dma_buf op.
680 file->f_path.dentry->d_fsdata = NULL;
685 module_put(exp_info->owner);
688 EXPORT_SYMBOL_NS_GPL(dma_buf_export, DMA_BUF);
691 * dma_buf_fd - returns a file descriptor for the given struct dma_buf
692 * @dmabuf: [in] pointer to dma_buf for which fd is required.
693 * @flags: [in] flags to give to fd
695 * On success, returns an associated 'fd'. Else, returns error.
697 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
701 if (!dmabuf || !dmabuf->file)
704 fd = get_unused_fd_flags(flags);
708 fd_install(fd, dmabuf->file);
712 EXPORT_SYMBOL_NS_GPL(dma_buf_fd, DMA_BUF);
715 * dma_buf_get - returns the struct dma_buf related to an fd
716 * @fd: [in] fd associated with the struct dma_buf to be returned
718 * On success, returns the struct dma_buf associated with an fd; uses
719 * file's refcounting done by fget to increase refcount. returns ERR_PTR
722 struct dma_buf *dma_buf_get(int fd)
729 return ERR_PTR(-EBADF);
731 if (!is_dma_buf_file(file)) {
733 return ERR_PTR(-EINVAL);
736 return file->private_data;
738 EXPORT_SYMBOL_NS_GPL(dma_buf_get, DMA_BUF);
741 * dma_buf_put - decreases refcount of the buffer
742 * @dmabuf: [in] buffer to reduce refcount of
744 * Uses file's refcounting done implicitly by fput().
746 * If, as a result of this call, the refcount becomes 0, the 'release' file
747 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
748 * in turn, and frees the memory allocated for dmabuf when exported.
750 void dma_buf_put(struct dma_buf *dmabuf)
752 if (WARN_ON(!dmabuf || !dmabuf->file))
757 EXPORT_SYMBOL_NS_GPL(dma_buf_put, DMA_BUF);
759 static void mangle_sg_table(struct sg_table *sg_table)
761 #ifdef CONFIG_DMABUF_DEBUG
763 struct scatterlist *sg;
765 /* To catch abuse of the underlying struct page by importers mix
766 * up the bits, but take care to preserve the low SG_ bits to
767 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf
768 * before passing the sgt back to the exporter. */
769 for_each_sgtable_sg(sg_table, sg, i)
770 sg->page_link ^= ~0xffUL;
774 static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach,
775 enum dma_data_direction direction)
777 struct sg_table *sg_table;
780 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
781 if (IS_ERR_OR_NULL(sg_table))
784 if (!dma_buf_attachment_is_dynamic(attach)) {
785 ret = dma_resv_wait_timeout(attach->dmabuf->resv,
786 DMA_RESV_USAGE_KERNEL, true,
787 MAX_SCHEDULE_TIMEOUT);
789 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
795 mangle_sg_table(sg_table);
800 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
801 * @dmabuf: [in] buffer to attach device to.
802 * @dev: [in] device to be attached.
803 * @importer_ops: [in] importer operations for the attachment
804 * @importer_priv: [in] importer private pointer for the attachment
806 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
807 * must be cleaned up by calling dma_buf_detach().
809 * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
814 * A pointer to newly created &dma_buf_attachment on success, or a negative
815 * error code wrapped into a pointer on failure.
817 * Note that this can fail if the backing storage of @dmabuf is in a place not
818 * accessible to @dev, and cannot be moved to a more suitable place. This is
819 * indicated with the error code -EBUSY.
821 struct dma_buf_attachment *
822 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
823 const struct dma_buf_attach_ops *importer_ops,
826 struct dma_buf_attachment *attach;
829 if (WARN_ON(!dmabuf || !dev))
830 return ERR_PTR(-EINVAL);
832 if (WARN_ON(importer_ops && !importer_ops->move_notify))
833 return ERR_PTR(-EINVAL);
835 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
837 return ERR_PTR(-ENOMEM);
840 attach->dmabuf = dmabuf;
842 attach->peer2peer = importer_ops->allow_peer2peer;
843 attach->importer_ops = importer_ops;
844 attach->importer_priv = importer_priv;
846 if (dmabuf->ops->attach) {
847 ret = dmabuf->ops->attach(dmabuf, attach);
851 dma_resv_lock(dmabuf->resv, NULL);
852 list_add(&attach->node, &dmabuf->attachments);
853 dma_resv_unlock(dmabuf->resv);
855 /* When either the importer or the exporter can't handle dynamic
856 * mappings we cache the mapping here to avoid issues with the
857 * reservation object lock.
859 if (dma_buf_attachment_is_dynamic(attach) !=
860 dma_buf_is_dynamic(dmabuf)) {
861 struct sg_table *sgt;
863 if (dma_buf_is_dynamic(attach->dmabuf)) {
864 dma_resv_lock(attach->dmabuf->resv, NULL);
865 ret = dmabuf->ops->pin(attach);
870 sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
872 sgt = ERR_PTR(-ENOMEM);
877 if (dma_buf_is_dynamic(attach->dmabuf))
878 dma_resv_unlock(attach->dmabuf->resv);
880 attach->dir = DMA_BIDIRECTIONAL;
890 if (dma_buf_is_dynamic(attach->dmabuf))
891 dmabuf->ops->unpin(attach);
894 if (dma_buf_is_dynamic(attach->dmabuf))
895 dma_resv_unlock(attach->dmabuf->resv);
897 dma_buf_detach(dmabuf, attach);
900 EXPORT_SYMBOL_NS_GPL(dma_buf_dynamic_attach, DMA_BUF);
903 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
904 * @dmabuf: [in] buffer to attach device to.
905 * @dev: [in] device to be attached.
907 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
910 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
913 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
915 EXPORT_SYMBOL_NS_GPL(dma_buf_attach, DMA_BUF);
917 static void __unmap_dma_buf(struct dma_buf_attachment *attach,
918 struct sg_table *sg_table,
919 enum dma_data_direction direction)
921 /* uses XOR, hence this unmangles */
922 mangle_sg_table(sg_table);
924 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
928 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list
929 * @dmabuf: [in] buffer to detach from.
930 * @attach: [in] attachment to be detached; is free'd after this call.
932 * Clean up a device attachment obtained by calling dma_buf_attach().
934 * Optionally this calls &dma_buf_ops.detach for device-specific detach.
936 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
938 if (WARN_ON(!dmabuf || !attach))
942 if (dma_buf_is_dynamic(attach->dmabuf))
943 dma_resv_lock(attach->dmabuf->resv, NULL);
945 __unmap_dma_buf(attach, attach->sgt, attach->dir);
947 if (dma_buf_is_dynamic(attach->dmabuf)) {
948 dmabuf->ops->unpin(attach);
949 dma_resv_unlock(attach->dmabuf->resv);
953 dma_resv_lock(dmabuf->resv, NULL);
954 list_del(&attach->node);
955 dma_resv_unlock(dmabuf->resv);
956 if (dmabuf->ops->detach)
957 dmabuf->ops->detach(dmabuf, attach);
961 EXPORT_SYMBOL_NS_GPL(dma_buf_detach, DMA_BUF);
964 * dma_buf_pin - Lock down the DMA-buf
965 * @attach: [in] attachment which should be pinned
967 * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
968 * call this, and only for limited use cases like scanout and not for temporary
969 * pin operations. It is not permitted to allow userspace to pin arbitrary
970 * amounts of buffers through this interface.
972 * Buffers must be unpinned by calling dma_buf_unpin().
975 * 0 on success, negative error code on failure.
977 int dma_buf_pin(struct dma_buf_attachment *attach)
979 struct dma_buf *dmabuf = attach->dmabuf;
982 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
984 dma_resv_assert_held(dmabuf->resv);
986 if (dmabuf->ops->pin)
987 ret = dmabuf->ops->pin(attach);
991 EXPORT_SYMBOL_NS_GPL(dma_buf_pin, DMA_BUF);
994 * dma_buf_unpin - Unpin a DMA-buf
995 * @attach: [in] attachment which should be unpinned
997 * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
998 * any mapping of @attach again and inform the importer through
999 * &dma_buf_attach_ops.move_notify.
1001 void dma_buf_unpin(struct dma_buf_attachment *attach)
1003 struct dma_buf *dmabuf = attach->dmabuf;
1005 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
1007 dma_resv_assert_held(dmabuf->resv);
1009 if (dmabuf->ops->unpin)
1010 dmabuf->ops->unpin(attach);
1012 EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, DMA_BUF);
1015 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
1016 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
1018 * @attach: [in] attachment whose scatterlist is to be returned
1019 * @direction: [in] direction of DMA transfer
1021 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
1022 * on error. May return -EINTR if it is interrupted by a signal.
1024 * On success, the DMA addresses and lengths in the returned scatterlist are
1025 * PAGE_SIZE aligned.
1027 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
1028 * the underlying backing storage is pinned for as long as a mapping exists,
1029 * therefore users/importers should not hold onto a mapping for undue amounts of
1032 * Important: Dynamic importers must wait for the exclusive fence of the struct
1033 * dma_resv attached to the DMA-BUF first.
1035 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
1036 enum dma_data_direction direction)
1038 struct sg_table *sg_table;
1043 if (WARN_ON(!attach || !attach->dmabuf))
1044 return ERR_PTR(-EINVAL);
1046 if (dma_buf_attachment_is_dynamic(attach))
1047 dma_resv_assert_held(attach->dmabuf->resv);
1051 * Two mappings with different directions for the same
1052 * attachment are not allowed.
1054 if (attach->dir != direction &&
1055 attach->dir != DMA_BIDIRECTIONAL)
1056 return ERR_PTR(-EBUSY);
1061 if (dma_buf_is_dynamic(attach->dmabuf)) {
1062 dma_resv_assert_held(attach->dmabuf->resv);
1063 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
1064 r = attach->dmabuf->ops->pin(attach);
1070 sg_table = __map_dma_buf(attach, direction);
1072 sg_table = ERR_PTR(-ENOMEM);
1074 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
1075 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1076 attach->dmabuf->ops->unpin(attach);
1078 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
1079 attach->sgt = sg_table;
1080 attach->dir = direction;
1083 #ifdef CONFIG_DMA_API_DEBUG
1084 if (!IS_ERR(sg_table)) {
1085 struct scatterlist *sg;
1090 for_each_sgtable_dma_sg(sg_table, sg, i) {
1091 addr = sg_dma_address(sg);
1092 len = sg_dma_len(sg);
1093 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
1094 pr_debug("%s: addr %llx or len %x is not page aligned!\n",
1095 __func__, addr, len);
1099 #endif /* CONFIG_DMA_API_DEBUG */
1102 EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment, DMA_BUF);
1105 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
1106 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1108 * @attach: [in] attachment to unmap buffer from
1109 * @sg_table: [in] scatterlist info of the buffer to unmap
1110 * @direction: [in] direction of DMA transfer
1112 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
1114 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
1115 struct sg_table *sg_table,
1116 enum dma_data_direction direction)
1120 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1123 if (dma_buf_attachment_is_dynamic(attach))
1124 dma_resv_assert_held(attach->dmabuf->resv);
1126 if (attach->sgt == sg_table)
1129 if (dma_buf_is_dynamic(attach->dmabuf))
1130 dma_resv_assert_held(attach->dmabuf->resv);
1132 __unmap_dma_buf(attach, sg_table, direction);
1134 if (dma_buf_is_dynamic(attach->dmabuf) &&
1135 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1136 dma_buf_unpin(attach);
1138 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment, DMA_BUF);
1141 * dma_buf_move_notify - notify attachments that DMA-buf is moving
1143 * @dmabuf: [in] buffer which is moving
1145 * Informs all attachmenst that they need to destroy and recreated all their
1148 void dma_buf_move_notify(struct dma_buf *dmabuf)
1150 struct dma_buf_attachment *attach;
1152 dma_resv_assert_held(dmabuf->resv);
1154 list_for_each_entry(attach, &dmabuf->attachments, node)
1155 if (attach->importer_ops)
1156 attach->importer_ops->move_notify(attach);
1158 EXPORT_SYMBOL_NS_GPL(dma_buf_move_notify, DMA_BUF);
1163 * There are mutliple reasons for supporting CPU access to a dma buffer object:
1165 * - Fallback operations in the kernel, for example when a device is connected
1166 * over USB and the kernel needs to shuffle the data around first before
1167 * sending it away. Cache coherency is handled by braketing any transactions
1168 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
1171 * Since for most kernel internal dma-buf accesses need the entire buffer, a
1172 * vmap interface is introduced. Note that on very old 32-bit architectures
1173 * vmalloc space might be limited and result in vmap calls failing.
1177 * void \*dma_buf_vmap(struct dma_buf \*dmabuf, struct iosys_map \*map)
1178 * void dma_buf_vunmap(struct dma_buf \*dmabuf, struct iosys_map \*map)
1180 * The vmap call can fail if there is no vmap support in the exporter, or if
1181 * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference
1182 * count for all vmap access and calls down into the exporter's vmap function
1183 * only when no vmapping exists, and only unmaps it once. Protection against
1184 * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex.
1186 * - For full compatibility on the importer side with existing userspace
1187 * interfaces, which might already support mmap'ing buffers. This is needed in
1188 * many processing pipelines (e.g. feeding a software rendered image into a
1189 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1190 * framework already supported this and for DMA buffer file descriptors to
1191 * replace ION buffers mmap support was needed.
1193 * There is no special interfaces, userspace simply calls mmap on the dma-buf
1194 * fd. But like for CPU access there's a need to braket the actual access,
1195 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1196 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1199 * Some systems might need some sort of cache coherency management e.g. when
1200 * CPU and GPU domains are being accessed through dma-buf at the same time.
1201 * To circumvent this problem there are begin/end coherency markers, that
1202 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1203 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1204 * sequence would be used like following:
1207 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1208 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1209 * want (with the new data being consumed by say the GPU or the scanout
1211 * - munmap once you don't need the buffer any more
1213 * For correctness and optimal performance, it is always required to use
1214 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1215 * mapped address. Userspace cannot rely on coherent access, even when there
1216 * are systems where it just works without calling these ioctls.
1218 * - And as a CPU fallback in userspace processing pipelines.
1220 * Similar to the motivation for kernel cpu access it is again important that
1221 * the userspace code of a given importing subsystem can use the same
1222 * interfaces with a imported dma-buf buffer object as with a native buffer
1223 * object. This is especially important for drm where the userspace part of
1224 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1225 * use a different way to mmap a buffer rather invasive.
1227 * The assumption in the current dma-buf interfaces is that redirecting the
1228 * initial mmap is all that's needed. A survey of some of the existing
1229 * subsystems shows that no driver seems to do any nefarious thing like
1230 * syncing up with outstanding asynchronous processing on the device or
1231 * allocating special resources at fault time. So hopefully this is good
1232 * enough, since adding interfaces to intercept pagefaults and allow pte
1233 * shootdowns would increase the complexity quite a bit.
1237 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1240 * If the importing subsystem simply provides a special-purpose mmap call to
1241 * set up a mapping in userspace, calling do_mmap with &dma_buf.file will
1242 * equally achieve that for a dma-buf object.
1245 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1246 enum dma_data_direction direction)
1248 bool write = (direction == DMA_BIDIRECTIONAL ||
1249 direction == DMA_TO_DEVICE);
1250 struct dma_resv *resv = dmabuf->resv;
1253 /* Wait on any implicit rendering fences */
1254 ret = dma_resv_wait_timeout(resv, dma_resv_usage_rw(write),
1255 true, MAX_SCHEDULE_TIMEOUT);
1263 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1264 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1265 * preparations. Coherency is only guaranteed in the specified range for the
1266 * specified access direction.
1267 * @dmabuf: [in] buffer to prepare cpu access for.
1268 * @direction: [in] length of range for cpu access.
1270 * After the cpu access is complete the caller should call
1271 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
1272 * it guaranteed to be coherent with other DMA access.
1274 * This function will also wait for any DMA transactions tracked through
1275 * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit
1276 * synchronization this function will only ensure cache coherency, callers must
1277 * ensure synchronization with such DMA transactions on their own.
1279 * Can return negative error values, returns 0 on success.
1281 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1282 enum dma_data_direction direction)
1286 if (WARN_ON(!dmabuf))
1289 might_lock(&dmabuf->resv->lock.base);
1291 if (dmabuf->ops->begin_cpu_access)
1292 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1294 /* Ensure that all fences are waited upon - but we first allow
1295 * the native handler the chance to do so more efficiently if it
1296 * chooses. A double invocation here will be reasonably cheap no-op.
1299 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1303 EXPORT_SYMBOL_NS_GPL(dma_buf_begin_cpu_access, DMA_BUF);
1306 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1307 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1308 * actions. Coherency is only guaranteed in the specified range for the
1309 * specified access direction.
1310 * @dmabuf: [in] buffer to complete cpu access for.
1311 * @direction: [in] length of range for cpu access.
1313 * This terminates CPU access started with dma_buf_begin_cpu_access().
1315 * Can return negative error values, returns 0 on success.
1317 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1318 enum dma_data_direction direction)
1324 might_lock(&dmabuf->resv->lock.base);
1326 if (dmabuf->ops->end_cpu_access)
1327 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1331 EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, DMA_BUF);
1335 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1336 * @dmabuf: [in] buffer that should back the vma
1337 * @vma: [in] vma for the mmap
1338 * @pgoff: [in] offset in pages where this mmap should start within the
1341 * This function adjusts the passed in vma so that it points at the file of the
1342 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1343 * checking on the size of the vma. Then it calls the exporters mmap function to
1344 * set up the mapping.
1346 * Can return negative error values, returns 0 on success.
1348 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1349 unsigned long pgoff)
1351 if (WARN_ON(!dmabuf || !vma))
1354 /* check if buffer supports mmap */
1355 if (!dmabuf->ops->mmap)
1358 /* check for offset overflow */
1359 if (pgoff + vma_pages(vma) < pgoff)
1362 /* check for overflowing the buffer's size */
1363 if (pgoff + vma_pages(vma) >
1364 dmabuf->size >> PAGE_SHIFT)
1367 /* readjust the vma */
1368 vma_set_file(vma, dmabuf->file);
1369 vma->vm_pgoff = pgoff;
1371 return dmabuf->ops->mmap(dmabuf, vma);
1373 EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, DMA_BUF);
1376 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1377 * address space. Same restrictions as for vmap and friends apply.
1378 * @dmabuf: [in] buffer to vmap
1379 * @map: [out] returns the vmap pointer
1381 * This call may fail due to lack of virtual mapping address space.
1382 * These calls are optional in drivers. The intended use for them
1383 * is for mapping objects linear in kernel space for high use objects.
1385 * To ensure coherency users must call dma_buf_begin_cpu_access() and
1386 * dma_buf_end_cpu_access() around any cpu access performed through this
1389 * Returns 0 on success, or a negative errno code otherwise.
1391 int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
1393 struct iosys_map ptr;
1396 iosys_map_clear(map);
1398 if (WARN_ON(!dmabuf))
1401 if (!dmabuf->ops->vmap)
1404 mutex_lock(&dmabuf->lock);
1405 if (dmabuf->vmapping_counter) {
1406 dmabuf->vmapping_counter++;
1407 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1408 *map = dmabuf->vmap_ptr;
1412 BUG_ON(iosys_map_is_set(&dmabuf->vmap_ptr));
1414 ret = dmabuf->ops->vmap(dmabuf, &ptr);
1415 if (WARN_ON_ONCE(ret))
1418 dmabuf->vmap_ptr = ptr;
1419 dmabuf->vmapping_counter = 1;
1421 *map = dmabuf->vmap_ptr;
1424 mutex_unlock(&dmabuf->lock);
1427 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, DMA_BUF);
1430 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1431 * @dmabuf: [in] buffer to vunmap
1432 * @map: [in] vmap pointer to vunmap
1434 void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map)
1436 if (WARN_ON(!dmabuf))
1439 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1440 BUG_ON(dmabuf->vmapping_counter == 0);
1441 BUG_ON(!iosys_map_is_equal(&dmabuf->vmap_ptr, map));
1443 mutex_lock(&dmabuf->lock);
1444 if (--dmabuf->vmapping_counter == 0) {
1445 if (dmabuf->ops->vunmap)
1446 dmabuf->ops->vunmap(dmabuf, map);
1447 iosys_map_clear(&dmabuf->vmap_ptr);
1449 mutex_unlock(&dmabuf->lock);
1451 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF);
1453 #ifdef CONFIG_DEBUG_FS
1454 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1456 struct dma_buf *buf_obj;
1457 struct dma_buf_attachment *attach_obj;
1458 int count = 0, attach_count;
1462 ret = mutex_lock_interruptible(&db_list.lock);
1467 seq_puts(s, "\nDma-buf Objects:\n");
1468 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\tname\n",
1469 "size", "flags", "mode", "count", "ino");
1471 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1473 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1478 spin_lock(&buf_obj->name_lock);
1479 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1481 buf_obj->file->f_flags, buf_obj->file->f_mode,
1482 file_count(buf_obj->file),
1484 file_inode(buf_obj->file)->i_ino,
1485 buf_obj->name ?: "<none>");
1486 spin_unlock(&buf_obj->name_lock);
1488 dma_resv_describe(buf_obj->resv, s);
1490 seq_puts(s, "\tAttached Devices:\n");
1493 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1494 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1497 dma_resv_unlock(buf_obj->resv);
1499 seq_printf(s, "Total %d devices attached\n\n",
1503 size += buf_obj->size;
1506 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1508 mutex_unlock(&db_list.lock);
1512 mutex_unlock(&db_list.lock);
1516 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1518 static struct dentry *dma_buf_debugfs_dir;
1520 static int dma_buf_init_debugfs(void)
1525 d = debugfs_create_dir("dma_buf", NULL);
1529 dma_buf_debugfs_dir = d;
1531 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1532 NULL, &dma_buf_debug_fops);
1534 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1535 debugfs_remove_recursive(dma_buf_debugfs_dir);
1536 dma_buf_debugfs_dir = NULL;
1543 static void dma_buf_uninit_debugfs(void)
1545 debugfs_remove_recursive(dma_buf_debugfs_dir);
1548 static inline int dma_buf_init_debugfs(void)
1552 static inline void dma_buf_uninit_debugfs(void)
1557 static int __init dma_buf_init(void)
1561 ret = dma_buf_init_sysfs_statistics();
1565 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1566 if (IS_ERR(dma_buf_mnt))
1567 return PTR_ERR(dma_buf_mnt);
1569 mutex_init(&db_list.lock);
1570 INIT_LIST_HEAD(&db_list.head);
1571 dma_buf_init_debugfs();
1574 subsys_initcall(dma_buf_init);
1576 static void __exit dma_buf_deinit(void)
1578 dma_buf_uninit_debugfs();
1579 kern_unmount(dma_buf_mnt);
1580 dma_buf_uninit_sysfs_statistics();
1582 __exitcall(dma_buf_deinit);